As DRAMs increase in memory cell density, there is a continuing challenge to maintain sufficiently high storage capacitance despite decreasing cell area. Additionally, there is a continuing goal to further decrease cell area. One principal way of increasing cell capacitance is through cell structure techniques. Such techniques include three-dimensional cell capacitors, such as trenched or stacked capacitors. Yet as feature size continues to become smaller and smaller, development of improved materials for cell dielectrics as well as the cell structure are important. Highly integrated memory devices are expected to require a very thin dielectric film for the 3-dimensional capacitor of cylindrically stacked or trenched structures. To meet this requirement, the capacitor dielectric film thickness may be at or below 10 Angstroms of equivalent SiO2 thickness.
Insulating inorganic metal oxide materials (such as ferroelectric materials, perovskite materials and dielectric oxides) are commonly referred to as “high k” materials due to their high dielectric constants, which make them attractive as dielectric materials in capacitors, for example for high density DRAMs and non-volatile memories. Using such materials can enable the creation of much smaller and simpler capacitor structures for a given stored charge requirement, enabling the packing density dictated by future circuit design. One such material is tantalum pentoxide (Ta2O5). Ta2O5 can, of course, also be used in fabrication of materials other than capacitor dielectrics and in circuitry other than DRAM.
The dielectric constant of tantalum pentoxide can vary in a range from about 25 to in excess of 100. Typical prior art methods of forming tantalum pentoxide result in an initial deposition in the amorphous phase, and which also results in dielectric constants in the lowest portions of the range. Accordingly, subsequent anneal processes are typically employed to convert the material to various crystalline phases to achieve a significantly higher dielectric constant than the amorphous phase. Typical amorphous deposition processes include low pressure chemical vapor deposition utilizing tantalum organometallics. One inorganic process for depositing amorphous tantalum pentoxide utilizes chemical vapor deposition that is plasma enhanced using TaF5 with an O2/H2 plasma.
While the invention was motivated in addressing the above issues and improving upon the above-described drawbacks, it is in no way so limited. The invention is only limited by the accompanying claims as literally worded (without interpretative or other limiting reference to the above background art description, remaining portions of the specification or the drawings) and in accordance with the doctrine of equivalents.